Combined master cylinder and stop light switch for hydraulic brake systems



NOV. 1, 1938- J w TE 2,134,902

COMBINED MASTER CYLINDER AND STOP LIGHT SWITCH FOR HYDRAULIC BRAKESYSTEMS Original Filed Nov 8, 1923 INVENTOR 05)? 7/2222??? Whiz? BY WWWW

ATTORNEYS Patented Nov. '1, 1938 UNITED, STATES PATENT OFFICE COMBINEDMASTER CYLINDER AND STOP LIGHT SWITCH FOR HYDRAULIC BRAKE SYSTEMS JohnWilliam White, Detroit, Mich, assignor, by

mesne assignments, to Bendix Products Corporation, a corporation ofIndiana rial No. 718,863

10 Claims. (01. 177-339) The invention relates to hydraulic vehiclebrake systems and forms a division of my co-pending applications forpatent, Serial No. 317,933, filed November 8, 1928, and Serial No.559,109, filed August 24, 1931. The subject matter 01 the application isthe combined master cylinder and stop light switch and it is the primaryobject of 4 the invention to obtain a construction in which the switchcan only be operated to show the light when the hydraulic brake systemis in operative condition for applying the brakes. It is a furtherobject to simplify the construction as hereinafter set forth.

In the drawing:

Fig. 1 is a diagrammatic view illustrating a system embodying thisinvention;

Fig. 2 is a sectional view on a large scale 01 the master cylinder bywhich pressure is applied upon the fluid in the system;

Fig. 3 is an end elevation of such cylinder; certain parts being brokenaway;

Fig. 4 is a section through the electric switch.

The brake system which embodies one application of this invention isillustrated in Fig. 1 as comprising a master cylinder A by whichpressure is applied to the fluid, a plurality of brake cylinders B bywhich the pressure on the fluid is transmitted to the wheels andconduits C connecting the master cylinder with the brake cylinders.Pressure is created in the master cylinder A by any suitable means as bya brake pedal D and the operation of the master cylinder actuates a stoplight E. The master cylinder A is separately illustrated in Figs. 2 and3 and as is shown, comprises a casing l suitably mounted upon a crosschannel member 2 of a motor vehicle, being secured thereto by bolts 3.Within the easlng I is a pumping chamber 4 and a reservoir or supplychamber 5 which chambers are connected by a port 6. At the forward orinner end of the chamber l are outlets 1 and 8, the outlet 7 leading tothe conduit C and thence to the brake cylinders 13 and the outlet 8receiving a stop light switch 9 by which the stop light E is controlled.

The switch 9 is substantially that set forth in my prior Patent No.1,840,340, issued January 12, 1932. As shown in Fig. 4, it comprises thecasing 9 having a threaded nipple 9* for engaging the outlet 8, and achamber within the casing containing a flexible diaphragm 9 peripherallyclamped by a ring 9 A cover of insulating material 9 closes the casingand terminal posts 9 are mounted on and project through this coverplate. 9 is a metallic bridge contact for electrically connecting theterminal posts 9 with each other. 9 is a spring for normally holding thebridge contact 9 away from the posts and against the flexible diaphragm9 The construction is such that when fluid within the pump chamber 4 isunder sufllclently high pressure the diaphragm 9 will be flexed and thebridge contact 9 pressed against the terminal posts 9 against thetension of the spring 9 The detailed construction of the master cylinderis not essential, but as shown a piston I0 is arranged within thechamber 4 and is "actuated by a brake lever D. The piston normally restsagainst a stop ring I I at the mouth of the chamber, being held in suchposition by a spring 12 attached to the lever D and anchored to thechannel member 2. A rod I 3 extends between the piston and the lever Dpassing through an aperture in the cross channel member 2 and beingpivotally attached to the piston and to the lever. Mounted on the innerend of the piston I0 is a flexible cup l6 preferably of rubber, securedin place by a screw l1 and washer la.

The chambers 4 and 5 are connected not only by the port 6 but also by apassage I9, the outer end of the piston I0 being cut away at 20 so thatthe passage 19 is open regardless of the position of the piston l0.Surrounding the inner end of the rod i3 is a boot 2i preferably conicaland of flexible material. The inner and larger end of the boot 2| isclamped between the casing I and the cross member 2 by the bolts 3, anannular recess 22 being formed in the outer wall of the casing toreceive the edge of the boot. The outer and small end of the boot isinverted as shown in Fig. 2 and wired or otherwise rigidly secured in arecess 23 on the rod l3. The ends of the boot are thus sealed and theinterior of the boot is in direct communication not only with thechamber 4 but also with the chamber 5 through the passage l9.

A filling orifice 24 entering the chamber 4 is provided in the casing land is sealed by a needle valve 25. Threaded into the storage chamber 5is a breather cap 26 having a passage 21 therethrough. The upper end ofthe passage 21 is open at all times to the atmosphere but across thelower end of the passage 21 is a disk 28 of rubber or other flexiblematerial, secured at its periphery to the cap 26 and provided withintersecting slots 29. The disk 28 normally closes the passage 21 butany vacuum in the chamber 5 will be broken or any excess in air pressuretherein will be relieved by a flexing of the disk and a consequentopening of the slots. One or more longitudinally extending grooves 30 inthe piston I allow liquid to enter the cylinder chamber 4 past the cupi6 when a minus pressure is set up in the chamber.

As the present invention relates to the master cylinder in combinationwith the fluid actuated electric switch, it will be unnecessary todescribe the entire brake system in detail. In operation, the actuationof the pedal D will move the piston in the chamber 4, expelling fluidthrough the orifice 1 and conduit C to the several wheeled cylinders,causing the actuation of the same and the application of the brakes.When the pressure upon the fluid in the chamber 4 is suflicient to applythe brakes, itwill also actuate the switch 9, moving the flexiblediaphragm 9 and bridge contact Si against the resistance of the spring9* and electrically connecting the terminal posts 9 If on the other handthrough some defect in the system the pressure in the chamber 4 isinsuflicient for operating the brakes, then it will also be insuiiicientto actuate the electric switch 9. Thus the switch 9 in addition to itsfunction of operating the stop light is an indicator of theoperativeness of the brake system. It is thus possible for the operatorto test his brakes when the car is standing still and if he is unable toactuate the switch 9 and display the light, he is assured that thebrakes are not in condition for use.

What I claim as my invention is:

1. In combination, a hydraulic brake system that includes a mastercontrol container, means for forcibly contracting at will the controlcontainer, liquid operated brakes, piping leading from the interior ofsaid master control container to said brakes, and an incompressibleliquid within and filling the master control container and the pipesleading therefrom to the brakes; an electric system that includes asource of current supply, a signal and an electric switch having amovable contact member controlled as to switch' opening and closingmovements by a positionable member of a switch control container; andsaid switch control container that provides said positionable member forcontrolling the switch opening and closing movements of the movablecontact according to pressure conditions of the incompressibleliquidwithin the switch control container; said switch control containerbeing in direct communication with the liquid containing space of thehydraulic brake system whereby upon force being applied in a manner toeffect a contracting of the master control container theresimultaneously results an increase in the pressure of the liquid andwhich increase of pressure is exerted against the movable member of theswitch control container as well as against the brake parts that areunder the direct influence of the incompressible liquid in the hydraulicbrake system.

2. In combination, a hydraulic brake system that includes an expansibleand contractible master control container, a foot pedal for forciblycontracting the same, liquid operated brakes, piping leading from theinterior of said master control container to said brakes and anincompressible liquid within and filling the master control containerand the pipes leading from the master container to the brakes; anelectric system that includes a source of current supply, a signal andan electric switch having a movable contact member for determining theopening and closing of said electric switch; and an expansible andcontractible switch control container which provides a movable memberfor positioning the movable contact according to pressure conditionswithin the switch control container; said switch control container beingin direct communication with the liquid containing space of thehydraulic brake system.

3. In combination, a hydraulic brake system that includes an expansibleand contractible master control container, means for forciblycontracting the same, liquid operated brakes, piping leading from theinterior of said master control container to said brakes, and anincompressible liquid within and filling the master control contalnerand the pipes leading therefrom to the brakes; an electric system thatincludes a source of current supply, a signal and an electric switchhaving a movable contact member; and an expansible and contractibleswitch control container which provides a movable member for positioningthe movable contact to switch opening and closing position according topressure conditions within the switch control container; said switchcontrol container being in direct communication with the liquidcontaining space or sections of the hydraulic brake system and operabletherefrom whereby upon force being exerted in a manner to effect acontracting of the master control container there is eifected asimultaneous increase in pressure that is exerted against the movablemember of the switch control container with a consequent positioning ofthe movable contact of the electric switch, and also an eifectiveoperation of the hydraulic brakes.

4. In a motor vehicle of the automobile type, the combination of ahydraulic brake system that is dependent for its functioning upon arelatively incompressible liquid contained and maintained within thesystem, and a signal means that includes a diaphragm having a liquidcontact with the hydraulic brake system and operable under the influenceof the liquid pressure in said hydraulic brake system to cause a givingof a signal when the liquid pressure is increased incident to theapplication of the brakes and to cause a discontinuance of the signalwhen the liquid pressure is decreased incident to the release .of thebrakes.

5. In a motor vehicle of the automobile type, the combination of ahydraulic brake system that is dependent for its functioning upon forcestransmitted through-a relatively incompressible liquid maintained withinthe system, an electrical circuit including a signal and a source ofcurrent supply, an electrical switch including a diaphragm having aliquid contact with the hydraulic brake system, said switch having oneof its contact members movable under the influence of pressure of theliquid in said hydraulic brake system on said diaphragm to make andbreak said circuit whereby incident to an application of the brakes thesignal is given and whereby incident to a release of the brakes there isa discontinuance of the signal.

6. In a motor vehicle of the automobile type, the combination of ahydraulic brake system within which the relatively incompressible liquidupon which the system is dependent for its functioning is maintained,and a signal system that includes and is dependent for its functioningupon a diaphragm having a liquid contact with the hydraulic brake systemand which diaphragm is under the influence of pressure of the liquid insaid hydraulic brake system for efiecting a giving of the signal whenthe pressure on the liquid is increased incident to the application ofthe brakes and for effecting a discontinuance of the signal incident toa release of the brakes.

7. In a motorvehicle of the automobile type, in combination, a hydraulicbrake system which is dependent for its functioning upon relativelyincompressible liquid continuously confined therein, and a signal meanshaving a diaphragm for controlling the giving and discontinuance of thesignal, which said diaphragm has liquid contact with the hydraulic brakesystem and is movable under the influence of'the pressure of the liquidin said hydraulic brake system so as to cause a giving of the signalincident to brake application and so as to cause a discontinuance of thesignal incident to brake release.

8. In an automobile, the combination of a hydraulic brake systemdependent for its functioning upon a suitable liquid maintained therein,

said system including brakes and a brake pedal operable to apply saidbrakes by hydraulic pressure, a signal, and means for controlling theoperating of said signal which said means com prises a diaphragm havinga liquid contact with the hydraulic brake system and positionable forcausing the signal to be given upon the applying of the brake and forcausing-a discontinuance of the signal upon the release of the brakes.

9. For use on an automobile, the combination of a hydraulic brakingsystem including a master cylinder and motorcylinders connected thereto,substantially incompressible hydraulic fluid contained in said systemand through which pressure is transmitted from said master cylinder tosaid motor cylinders, a signal, and means for controlling the operationof said signal dependent upon pressure in said substantiallyincompressible hydraulic fluid.

10. In an automobile, the combination of a hydraulic brake systemdependent for its functioning upon a substantiallyincompressiblesuitable liquid contained therein, said system includingbrakes and a brake pedal operable to apply said brakes by hydraulicpressure, a signal, and means for controlling the operation of saidsignal comprising an element positionable for causing the signal to begiven upon the applying of the brakes and for causing a discontinuanceof the signal upon the release of the brakes.

JOHN WILLIAM WHITE.

